Steve Tilley, QMI Agency

Call of Duty is not so much a video game series as an all-out entertainment juggernaut, one that's generated over $6 billion in sales since its debut a decade ago.

Not surprisingly, any new installment in the guns-a-blazing franchise is a pretty big deal, roughly on the order of a new Marvel superhero movie. Except the games usually make even more money.

Tuesday marks the release of Call of Duty: Ghosts, which lands on the Xbox 360, PlayStation 3, Wii U and Windows PCs. Versions for the upcoming Xbox One and PlayStation 4 consoles will be available on those machines' launch dates, Nov. 15 and Nov. 22 respectively.

For those who don't know a killstreak from a strike chain but would like to have some clue why their friends/coworkers/kids are so excited this week, here's a quick primer on the mother of all shooters.

It's set in different time periods

The original Call of Duty games took place during World War II, until 2007's Call of Duty 4: Modern Warfare brought the action into the present day. Since then, the series has visited the Cold War as well as the near future, with Ghosts taking place primarily in 2023.

Many gamers - if not most - play Call of Duty online

Although each game has a solo storyline that puts players in the combat boots of heroic soldiers, it's the comprehensive and addictive online multiplayer modes that are the main draw for the many fans who love gunning each other down on virtual fields of battle. Ghosts brings several new features and tweaks to its online offerings.

It makes tons of money

Sales of Call of Duty games are often expressed in how long it took to hit $1 billion worth of copies sold. Call of Duty: Modern Warfare 3 reached that number 16 days after its 2011 release, while last year's Call of Duty: Black Ops II notched it in 15 days.

It's facing some tough competition

Although Ghosts will surely sell very well, Call of Duty publisher Activision is going head-to-head with rival EA's Battlefield 4, which came out last week. EA's sci-fi shooter Titanfall, which is being designed by former Call of Duty developers, is also expected to take a bite out of the Ghosts fanbase when it debuts on the Xbox and PC next March.

It courts controversy

Aside from the general violent nature of the game and the (not entirely untrue) perception that online players can be a horribly foul-mouthed lot, Call of Duty has pushed the boundaries of what interactive entertainment can get away with. An infamous scene in 2009's Call of Duty: Modern Warfare 2 had players infiltrating a heavily armed Russian terrorist group that massacres civilians at an airport. Like most games in the series, Ghosts is intended for players 17 and older.

It goes on sale Monday night

Many retailers, including most Future Shop and Best Buy locations, will hold special late-night openings to start selling the game at 12:01 a.m. Tuesday. Tell the Call of Duty fans in your life to dress warm if they go, because it's hard to game with frostbitten thumbs.